Check out the Design Configuration section of the dev docs step #4. docs.magento.com/m2/2.1/ce/user_guide/design/configuration.h‌​tml. I've yet to try this feature before but it appears to me that is along the lines of what you're asking for.

Main advantage of sales_order_place_after event is that it is called from front end checkout or when creating an order on admin.

This page of the Magento dev docs walks you through basic style changes. I strongly suggest reviewing that guide. Afterwards, work on setting up Grunt. It's really simple to do and will change your life.

Why not inject the collection factory instead?

This works. System.xml should live in Vendor/ModuleName/etc/adminhtml/system.xml.

Visit Magento's dev docs and make certain that your permissions are set correctly.

You should have to do nothing more than select yes from the dropdown to enable it, as it's included with Magento by default, and then clear the configuration and page cache types on the Cache Management page in the admin. Is this a clean install? Any error logs in var/log directory?

I just tried it on my local machine and it does work, but I am running 2.1.1. I'll try again on a 2.1.0 install and report back. BTW, the command I ran was bin/magento admin:user:create --admin-user=testuser --admin-password=123456q [email protected] --admin-firstname=firstname --admin-lastname=lastname .

You can track your order from that link. What exactly are you asking if that doesn't work?

Magento 2 has an "Orders and Returns" link in the footer.

I added a new role and set it to custom permissions and the tree exists. Is this a default/clean install? Can you show log files? Have you enabled any new extensions?